Meso and Macrofauna Responses to Biochar in Urban Soils

Abstract

Anthropogenic soils are becoming more prominent across the globe, often seen in urban areas, and ecological soil management presents an opportunity to shift from big business to ecosystem services focusing on local food provision, stormwater management, etc., and resident autonomy, highlighting the need to alleviate continued degradation on urban soils. Among many agricultural soil amendments biochar, a form of charcoal, has numerous favorable qualities including water storing capabilities, plant nutrients retention, and carbon sequestration, as well as potentially positive impacts on soil microbial communities. The particle sizes of biochars vary greatly, and little consensus exists on what size, if any, explains best optimization of biochar functions in soil and what effects this application may have on soil fauna and the processes they carry out. The effect of biochar application on soil invertebrates, specifically arthropods, have not been thoroughly investigated despite increasing recognition that soil fauna, micro-, meso-, and macro- all play key roles in soil health and quality. In this study, we applied 3 distinct particle size distributions of biochar together with compost in treatments across 64 plots. We collected soil invertebrates using pitfall traps to determine faunal responses to biochar application rate and particle size after an initial growing season. We saw significant results in moisture depending on biochar treatment with Mixed showing the highest and Small particles appearing to account for the effects more than Large. Other results suggest no significant difference in faunal responses, specifically relative abundance, diversity, and community composition, to the first season of biochar application. Species richness analysis suggests there are marginally significant trends towards a certain particle size, with Small (sieved; <1mm) treatments collecting the most invertebrates and Mixed (unsieved) treatments suggesting below ground influences, which may also be seen with biomass. This study provides key metrics needed to inform ecological management using biochar, and serves as a model for urban ecology literature, and a model for testing hypotheses about invertebrate community responses to biochar application in urban agricultural settings.